1. Field of the Invention
The present invention relates to a punch press, and, in particular, to a punch press wherein it is possible to reliably cause a blank or a scrap punched from a workpiece to drop from the die hole of the die, and wherein the sliding section of the punch set can be automatically lubricated.
2. Description of the Prior Art
Conventionally, when a punching process utilizing a punch set and a die mounted on a punch press is performed, a blank or scrap punched from the workpiece once in a while does not drop down from the die hole of the die, but follows the elevation of the punch and rises on the upper surface of the die. In such a case, when the next punching process occurs, it can happen that the punching process is performed to the workpieces on which the scrap is piled up, presenting the possibility of damage to the punch set and die.
Accordingly, the technology has been developed wherein, when the punching process takes place, in order to cause the scrap and the like to reliably fall from the die hole, a fluid jet orifice is provided in the punch set on the centerline of the shaft of the punch, and a fluid feed orifice for freely communicating with the fluid jet orifice is provided on a ram which strikes the punch. When the ram reaches the vicinity of its lowest point compressed fluid is expelled from the fluid jet orifice of the punch and the scrap and the like is caused to drop from the die hole (For example, in Japanese Utility Model Publication No. Sho-55-5887).
However, in conventional configurations, a connecting orifice connecting to a pressure source is provided in a ram guide section for guiding the vertical action of the ram so that when the ram reaches the vicinity of its lowest point the connecting orifice communicates with the fluid feed orifice provided in the ram. Specifically, the timing of the feeding of the compressed fluid to the fluid jet orifice of the punch through the fluid feed orifice of the ram is unadjustable.
Accordingly, in the case where the height of the punch differs for each punch set, for example, and in the case where the punch becomes slightly shortened as a result of wear and repolishing, there is no compensation for the volume of the compressed fluid corresponding to the shortened portion, even though this is necessary; i.e. because the feed timing of the compressed fluid is constant, the compressed fluid becomes inadequate, and the dropping of the scrap and the like from the die becomes unreliable, leading to problems.
In addition, in the case, for example, where the workpiece is punched consecutively by a punch with a square cross section and a slot is formed, i.e. a nibbling process is carried out on the workpiece, the width of the punched hole part is minutely reduced when next punching process is carried out; therefore, a string-shaped residue is adhering to the peripheral surface of the punch. This residue may drop onto the top surface of the workpiece, and when the workpiece is punched, the problem arises that applying pressure by means of the punch guide or a stripper produces damage on the top surface of the workpiece.
Further, in a conventional punch set, when the sliding sections between the punch and the punch guide, and between the punch guide and the punch holder and the like, are lubricated prior to using the punch. However, there are occasions when lubricant is not used. Accordingly, there are cases where the lubrication of the sliding parts of the punch guide is inadequate.